This invention relates to a scroll compressor with a drive providing capacity modulation by reverse rotation of the motor.
Scroll compressors are becoming widely utilized in refrigerant compression applications. Scroll compressors consist of a pair of interfitting wraps which move relative to each other to compress a refrigerant.
While scroll compressors are becoming very popular, there are some design challenges. One design challenge with scroll compressors relates to controlling the output volume, or capacity, of the scroll compressor.
The volume of the compression chambers is relatively static, thus it is not easy to change capacity by changing the volume of the chambers. Nor is it easy to change volume by changing the speed of the motor, as this would require an expensive motor and control.
Most simple electrical motors utilized in scroll compressors are reversible. However, a scroll compressor cannot typically be driven in reverse for any length of time without resulting in some undesirable characteristics.
It would be desirable to achieve capacity control with a simple reversible electrical motor.
Several embodiments are disclosed wherein a reversible motor rotates in a first direction and drives a shaft and an orbiting scroll to orbit relative to a fixed, or non-orbiting, scroll. This orbiting will be at a first high rate which is roughly equal to the motor speed. Of course, the orbiting scroll orbits while the motor shaft rotates. However, the motor shaft speed revolutions will be approximately equal to the orbiting cycles of the orbiting scroll during forward rotation.
On the other hand, when capacity modulation is desired, the motor is caused to be driven in a reverse direction. An appropriate drive connection between the shaft and the orbiting scroll will no longer drive the orbiting scroll at the first rate. Instead, a reduced speed is achieved when the motor is driven in the reverse direction. A transmission ensures the orbiting scroll is still driven in the forward direction even though the motor is being driven in the reverse direction.
In two embodiments, a system of roller clutches transmits drive directly from the motor to the orbiting scroll shaft when the motor is driven in a forward direction. However, when the motor is driven in a reverse direction, the roller clutches actuate a gear reduction, and in a preferred embodiment, a planetary gear reduction such that the speed of the orbiting scroll is reduced. Preferably, the speed is reduced to approximately 30%-70%, and in one embodiment 50% of the speed in the forward direction.
In one embodiment, the planetary gear system is provided between the shaft and the motor roller. In this embodiment, the counterweights can function as normal.
In a second embodiment, the planetary transmission is disposed between the shaft, and an eccentric for driving the orbiting scroll.
In a third embodiment, a gear reduction is not utilized. Instead, a ratchet device is utilized which will only drive the orbiting scroll a portion of the time when the motor is driven in reverse. During the other half, rotation will not drive the crank pin such that it will slip, and not cause rotation of the orbiting scroll.
The disclosed embodiments are somewhat exemplary. The main aspect of this invention relates to the use of a transmission to provide two levels of capacity by reversing the motor drive direction. These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.